The present invention relates to a gas quick water heater, and more particularly, to a gas quick water heater which employs a counter-flow method in which the direction of heat flow is opposite to the direction of water flow to be heated, and which indirectly heats a heat exchanger.
A general gas quick water heater, as shown in FIG. 1, directly heats a heat exchanging tube 2, through which cold water introduced through a water supply pipe 1 flows, with a burner 3 so that the cold water is heated. The heated water is supplied via a hot-water pipe 4.
However, in such a gas quick water heater, the flame of burner 3 is applied directly to heat exchanging tube 2 which is corroded due to high temperature, shortening the life of the gas quick water heater. Further, the heater has no means for completely burning harmful gas such as carbon monoxide and nitrogen oxide produced during a gas combustion, thereby decreasing the combustion efficiency and creating environmental pollution. This is dangerous for poisoning due to the harmful gases. Moreover, in the heater, the heat of burner 3 is designed to focus on the fin of short-length heat exchanging tube 2 and transmit the heat of the fin to water via heat exchanging tube 2, thereby increasing a heat loss.
Furthermore, the hot water discharged from hot-water pipe 4 cannot be supplied at more than one temperature. However, a temperature of hot water in taking a shower and a temperature of hot water in washing dishes are different. Therefore, it is desirable that when taking a shower and washing dishes at the same time, the hot water discharged from heat exchanging tube 2 should be supplied at two different temperatures. Since the conventional gas quick water heater supplies hot water at a single temperature, it is uneconomic to supply high-temperature hot water even in washing dishes. However, lower-temperature hot water can be used in washing dishes.
U.S. Pat. No. 5,365,887 discloses a gas quick water heater in which a heat exchanger is indirectly heated in a counter-flow method, heating cold water at a higher heat efficiency and thereby increasing the life of the heat exchanger. However, this heater does not overcome other problems and has not improved sharply heat efficiency and the life of heat exchanger.